1. Field of the Invention
The present invention pertains to a solid oxide fuel cell apparatus, and more particularly to a solid oxide fuel cell apparatus fitted with a steam generator on the outside portion of a module case housing multiple fuel cells.
2. Description of the Related Art
Solid oxide fuel cell apparatuses (“SOFCs” below) are fuel cells which operate at a relatively high temperature in which, using an oxide ion-conducting solid electrolyte as electrolyte, with electrodes attached to both sides thereof, fuel gas is supplied to one side thereof and oxidizer gas (air, oxygen, or the like) is supplied to the other side thereof.
Patent Document 1 (Japanese Unexamined Patent Application Publication No. 2012-221659) sets forth a cell-burner type of solid oxide fuel cell apparatus in which multiple individual fuel cells are disposed in a module case, fuel gas (off gas) remaining without being used for electrical generation is combusted at the top of these multiple individual fuel cells, and a reformer inside the module case is heated by this combustion heat. In particular, in the Patent Document 1 solid oxide fuel cell apparatus, from the standpoint of suppressing the degradation of temperature rise performance relative to the temperature inside the module in the startup step, or temperature unevenness (thermal unevenness) in the fuel cell module caused by the robbing of surrounding heat by a steam generator (vaporizer) for producing steam supplied to a reformer, the steam generator is placed inside the heat insulating material on the outside of the module case.